Abstract
In order to investigate the behaviour of dynamic switching, the flow is visualized with the smoke generated by soaking dry ice in hot water at about 50°C. As a cover plate, a glass plate with 3mm thickness dipped in 3% soapsuds is used to avoid the condensation of waterdrop.
Small scale models (80×60×10) are employed and a single pulse with small overshoot is used as the input signal.
A high speed cine camera (2000 frames/sec) is used to photograph the switching behaviours by using the smoke as the main jet. The relation between the switching caused by pressure and that by flow is investigated.
The obtained results can be summarized as follows.
1) The estimated control flow in the dynamic switching is less than that in the static switching. Therefore, it can be thought that the switching depends only on the strength of the control pressure pulse. The pulse width does not affect the switching.
2) The attachment point does not necessarily move downward until the detachment of the main jet occurs. And the new attachment point does not increase in proportion to time.
3) The output pressure reaches its maximum value long before the switching of flow finishes.
4) The transient switching may be divided into five phases.
